Thermo-electric auxiliary power unit

ABSTRACT

An auxiliary power unit disclosed. The auxiliary power unit includes an exhaust passage configured to direct a flow of exhaust from a primary mover, a catalyst substrate disposed within the exhaust passage, and a heater configured to heat the catalyst substrate. The auxiliary power unit also includes a cooling jacket associated with the exhaust passage. The auxiliary power unit further includes a thermo-electric device disposed between the cooling jacket and the exhaust passage. The thermo-electric device is configured to generate electrical power from a temperature gradient created by the heater and the cooling jacket when the primary mover is non-operational.

TECHNICAL FIELD

This disclosure relates generally to an auxiliary power unit, and more particularly to an auxiliary power unit utilizing thermo-electric devices associated with an exhaust flow.

BACKGROUND

Long distance haul machines such as on-highway trucks often power on-board electric loads associated with the comfort of an operator, as the machine parks overnight. The loads, commonly termed hotel loads, can include a television, a heater/air conditioner, a refrigerator, a DVD/VHS player, lights, etc. Traditionally, hotel loads have been powered by an auxiliary power unit and/or the primary mover when operating at low idle. If the primary mover is employed to power hotel loads, large quantities of fuel are consumed causing the generation of power to be inefficient. Idling of the primary mover also generates undesired noise. Typical auxiliary power units on the market consist of a small internal combustion engine drivingly coupled to an electric generator. These auxiliary power units, although quieter and more efficient than operating the primary mover, are still sub-optimal and expensive. An alternative type of auxiliary power unit can include a thermo-electric generator, which provides electrical power generated from the primary mover's waste heat, such as, for example, from the primary mover's exhaust.

A thermo-electric generator can be placed in or near an exhaust stream of a primary mover to convert a portion of the exhaust heat to electrical power. Specifically, the exhaust heat is applied to one side of a thermo-electric material, while an opposing side of the thermo-electric material is cooled to maintain a temperature gradient across the material. The temperature gradient is used to generate a voltage potential directed to power the hotel loads.

One example of producing electrical power utilizing a thermo-electric generator is described in U.S. Patent Publication No. 2003/0223919 (“the '919 publication”) issued to Kwak et al. on Dec. 4, 2003. The '919 publication discloses a supplemental energy generating system having a thermo-electric generator disposed between a coolant channel and a housing. The housing encloses a catalytic substrate and defines an exhaust passage for an engine to expel waste heat/exhaust. The thermo-electric generator is positioned to be in a heat exchange relationship with the catalytic substrate and the coolant channel, and to generate an electrical current as a function of the heat exchange. A processing system connected to the thermo-electric generator processes the electrical current and generates a power output. In this configuration, as long as the engine is running, electrical power generated from the exhaust may be used to power loads.

Although the supplemental energy system of the '919 publication may be beneficial in generating electrical power from waste heat, it may have limited use for supplying power to hotel loads. That is, because the system of the '919 publication relies on heat generated from the exhaust of the engine, once the engine is shut off the heat quickly dissipates and little or no power may be available. And, since hotel loads require power when the main engine is shut down (i.e., at night when the vehicle is not powered), the system of the '919 publication may not be applicable to long distance haul machines having hotel loads. The supplemental energy system of the '919 publication may also suffer from low efficiencies due to the use of bulk thermo-electric materials (i.e., thermo-electric materials with a figure of merit less than 1).

The disclosed auxiliary power unit is directed to overcoming one or more of the shortcomings set forth above.

SUMMARY

One aspect of the present disclosure is directed to an auxiliary power unit. The auxiliary power unit may include an exhaust passage configured to direct a flow of exhaust from a primary mover, a catalyst substrate disposed within the exhaust passage, and a heater configured to heat the catalyst substrate. The auxiliary power unit may also include a cooling jacket associated with the exhaust passage, and a thermoelectric device disposed between the cooling jacket and the exhaust passage. The thermoelectric device may be configured to generate electrical power from a temperature gradient created by the heater and the cooling jacket when the primary mover is non-operational.

Another aspect of the present disclosure is directed to a method of generating auxiliary power. The method may include generating heat to warm an exhaust treatment device and directing the heat toward a thermo-electric material when an associated primary mover is non-operational. The method may also include cooling the thermoelectric material to produce a temperature gradient. The method may further include generating electrical power from the temperature gradient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial illustration of an exemplary disclosed machine;

FIG. 2 is a diagrammatic illustration of an exemplary disclosed auxiliary power unit that may be used with the machine of FIG. 1; and

FIG. 3 illustrates a diagrammatic illustration of an exemplary disclosed thermo-electric device that may be used with the auxiliary power unit of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary machine 100. The machine 100 may refer to any type of fixed or mobile machine that performs some type of operation associated with a particular industry, such as, for example, mining, construction, farming, transportation, etc. Non-limiting examples of the mobile machine 100 may include on-highway trucks, earth moving vehicles, mining vehicles, agricultural vehicles, marine vessels, and/or any other type of machine. Further, the machine 100 may be conventionally powered and/or embody a hybrid-electric powered machine. For the purposes of this disclosure, the machine 100 is depicted as a long distance haul truck. It is also contemplated that the machine 100 may embody a generator set, a pump, or another stationary operation-performing machine.

The machine 100 may include a sleeper 102 configured to provide a rest area for an operator of the machine 100. The machine 100 may include one or more electrically-powered devices 106 associated with or disposed within the sleeper 102 and/or the machine 100. The devices 106 may include, for example, an air conditioner, a heater, a radio, a television, a refrigerator and/or any type of device associated with the needs and/or comforts of the operator. The devices 106 may be electrically connected to at least one power supply 104. It is contemplated that the devices 106 may be external of the sleeper 102 and/or the machine 100, and may embody various types of electric tools that may be coupled and/or un-coupled to the power supply 104.

The power supply 104 may embody, for example, a battery that serves as the primary source of electrical storage for the machine 100. Alternatively, the power supply 104 may include multiple batteries, capacitors, or other storage devices that serve as electrical storage for different systems and/or devices of the machine 100. The machine 100 may further include an auxiliary power unit 200 configured to generate electrical power while the machine 100 is non-operational. It is contemplated that the auxiliary power unit 200 may also generate electrical power during operation of the machine 100.

The machine 100 may include an engine 108 configured to produce a power output directed toward moving the machine 100 and/or toward satisfying the energy demands of the devices 106. The engine 108 may function as the primary mover of the machine 100 and is depicted and will be described as an internal combustion engine such as, for example, a diesel engine, a gasoline engine, and/or a gaseous fuel-powered engine. The engine 108 may be associated with one or more systems that facilitate the production of power. In particular, the engine 108 may include a cooling system 110 and an exhaust system 116. It is contemplated that the machine 100 may include additional systems, such as, for example, an air induction system, a fuel system, a lubrication system, a transmission system, a control system, a hydraulic system, and other such engine or machine systems known in the art.

The cooling system 110 may cool fluids (e.g. air, oil, and/or coolant) that are circulated throughout the sleeper 102, the engine 108, and/or the auxiliary power unit 200. The cooling system 110 may include, among other things, a heat exchanger 112 fixed to the machine 100 and configured to cool the fluids. The heat exchanger 112 may embody, for example, a tube and a shell type heat exchanger, a plate type heat exchanger, or any other type of heat exchanger known in the art. In one example, the heat exchanger 112 may be a liquid-to-air exchanger connected to the engine 108 via a coolant line 114. Alternatively or additionally, the heat exchanger 112 may condition a heat transferring medium supplied to a transmission oil cooler, a brake oil cooler, or any other cooling component of the machine 100. It is contemplated that the cooling system 110 may include additional heat exchangers and/or one or more pumps (not shown) to pressurize and circulate fluid throughout the machine 100. In one example, the one or more pumps (not shown) may be electrically-powered pumps configured to draw power from the power supply 104 while the engine 108 is operational and non-operational.

The exhaust system 116 may be configured to direct exhaust gas from the engine 108 to the atmosphere and reduce the amount of harmful constituents within the expelled exhaust gas. The exhaust system 116 may include, among other things, a catalyst substrate 120 disposed within an exhaust passage 118, and a heater 122 disposed upstream of the catalyst substrate 120 and being configured to heat the catalyst substrate 120. The exhaust passage 118 may include a configuration of pipes or other components that facilitate the movement of exhaust from the engine 108 to the catalyst substrate 120.

The catalyst substrate 120 may be made from a variety of materials that provide a mechanism for trapping particulate matter, which is subsequently combusted. For example, the catalyst substrate 120 may include a support material and a metal promoter, such as, for example, silver metal, dispersed within the catalyst support material. The support material may include one of alumina, zeolite, aluminophosphates, hexaluminates, aluminosilicates, zirconates, titanosilicates, and titanates. Combinations of these materials may be used and the support material may be chosen based on the type of fuel burned by the heater 122, a reductant used (if any), a desired air to fuel-vapor ratio, and/or for conformity with environmental standards. One of ordinary skill in the art will recognize that numerous other catalyst compositions may be used without departing from the scope of this disclosure. Further, multiple catalytic devices may be included with the exhaust system 116, if desired.

The heater 122 may be configured to raise the temperature of the catalyst substrate 120 for the purposes of combusting particulate matter trapped therein (i.e., to regenerate the catalyst substrate 120) or for enhancing the operation of the catalyst substrate 120. It is contemplated that the heater 122 may embody any configuration known in the art utilizing fuel injection/ignition technology. The heater 122 may be fluidly connected to receive fuel from an electronically-powered fuel pumping arrangement 124. The heater 122 may inject the fuel received from the pumping arrangement 124 toward the catalytic substrate 120 and be configured to regulate ignition and combustion of the injected fuel. The heater 122 may also be configured to adjust the quantity, pressure, and injection timing of the fuel directed toward the catalytic substrate 120. In one example, the heater 122 may be configured to draw electricity from the power supply 104 to ignite the fuel while the engine 108 is either operational or non-operational.

The fuel pumping arrangement 124 may embody a source of pressurized fuel. It is contemplated that the fuel pumping arrangement 124 may include one or more pumps, filters, valves, and/or fluid lines to facilitate the operation of the fuel pumping arrangement 124, if desired. In one example, the fuel pumping arrangement 124 may include an electric pump configured to draw electrical power from the power supply 104 while the engine 108 is either operational or non-operational. Additionally, it is contemplated that the fuel pumping arrangement 124 may supply fuel to the engine 108, if desired.

As shown in FIG. 2, the auxiliary power unit 200 may be associated with and/or include multiple components that cooperate to generate electrical power. Specifically, the auxiliary power unit 200 may be associated with the exhaust passage 118, the catalytic substrate 120, the heater 122, and the cooling system 110. Additionally, the auxiliary power unit 200 may include a cooling jacket 202, a thermo-electric device 204, a power bus 206, a power converter 208, and a controller 210. It is contemplated that the auxiliary power unit 200 may also include a dedicated air supply (not shown) that may mix pressurized combustion air with the injected fuel to be ignited by the heater 122. In one example, the dedicated air supply (not shown) may include an electric-powered air pump (not shown) driven by the power supply 104 to pressurize the air supply, and/or a storage tank (not shown) that may be filled by conventional compressors during operation of the engine 108. The auxiliary power unit 200 may create a temperature gradient between the exhaust passage 118 and the cooling jacket 202. A thermo-electric couple 300, configured to utilize the temperature gradient to convert thermal energy to electrical energy, may be included with the thermoelectric device 204 and disposed between the cooling jacket 202 and the exhaust passage 118. It is contemplated that the thermo-electric device 204 may include a plurality of thermo-electric couples, if desired.

The cooling jacket 202 may be configured to receive and circulate coolant received from the heat exchanger 112 via a coolant line 212. The cooling jacket 202 may generally surround the exhaust passage 118 and the thermo-electric couple 300, and may be configured in any way known in the art to pass a coolant therein while serving as a heat sink for the thermoelectric device 204. For example, the cooling jacket 202 may consist of one or more tubes coiled around the thermo-electric couple 300, the exhaust passage 118, and/or around the thermo-electric device 204 from one portion of the exhaust passage 118 to another. Alternatively, the cooling jacket 202 may consist of one or more tubes running substantially parallel to the exhaust passage 118. The cooling jacket 202 may also embody a singular cavity connected to one or more of the coolant lines 212 to introduce and/or remove coolant from the cooling jacket 202.

The thermoelectric device 204 may utilize the temperature gradient to generate a voltage on an output/input terminal 216. The output/input terminal 216 of the thermo-electric device 204 may be further coupled with an input/output terminal 218 of the power converter 208, such that the voltage generated by the thermo-electric device 204 may be converted by the power converter 208 to an output voltage on an output/input terminal 220 at a desired level (e.g., 14.4V, 30V, 300V, etc.). The output voltage on terminal 220 of the power converter 208 may then be applied to the power bus 206 to be used by other systems (not shown) of the machine 100.

The thermo-electric device 204 may be operated according to the Seebeck effect or the Peltier effect. FIG. 3 illustrates an exemplary configuration of thermo-electric materials operating according to the Seebeck effect. As shown in FIG. 3, the thermo-electric materials may be semiconductors that are packaged within the thermo-electric couple 300. The thermo-electric couple 300 may include a positive-type P element 302 and a negative-type N element 304. The thermo-electric couple 300 may also include a plurality of junctions 306, 308, and 310. Electrical power may be generated and passed through an electrical load 314 if a temperature gradient ΔT is maintained between junction 310 and junctions 306, 308 of thermo-electric couple 300. A heat source may be provided at one junction and a heat sink may be provided at the other junctions to create the temperature gradient ΔT.

The effectiveness of the thermo-electric material in converting heat energy to electrical energy (conversion efficiency “i”) may depend on the material's figure of merit termed “Z” and the average operating temperature “T”. The material's figure of merit termed “Z” is a material characteristic that is defined according to Eq. 1 below:

$\begin{matrix} {{Z = \frac{S^{2}\sigma}{\lambda}},} & {{Eq}.\mspace{14mu} 1} \end{matrix}$

-   -   wherein:     -   the S is the Seebeck coefficient of the material;     -   the σ is the electrical conductivity of the material; and     -   the λ is the thermal conductivity of the material.

Because the figure of merit Z may change as a function of temperature T, the figure of merit Z may be reported along with the temperature T, at which the properties are measured. Thus, the dimensionless product ZT may be used instead of the figure of merit Z to reflect the effectiveness of the thermo-electric material. To improve the desired COP or η of thermo-electric materials, an increase in the product ZT may be necessary.

From the definition of the figure of merit Z provided above, it can be seen that an independent increase in the Seebeck coefficient and/or electrical conductivity, or an independent decrease in the thermal conductivity, may contribute to a higher ZT. Conventional low ZT thermo-electric materials, also known as bulk thermo-electric materials, may have ZT values less than one (ZT<1). The described thermo-electric materials may have low dimensional structures with a higher figure of merit ZT, which may be approaching 10 (i.e., ZT≈10). These materials may include zero-dimensional quantum dots, one-dimensional nano wires, two-dimensional quantum wells and superlattice thermo-electric structures.

While bulk thermo-electric materials may be used in the thermo-electric device 204, in certain embodiments, the high ZT thermo-electric materials may also be used. High efficiency thermoelectric materials that have ZT values between about 1 and 10 may be provided consistent with disclosed embodiments. Additionally, it is contemplated that the thermo-electric materials may have a ZT value exceeding 10. In one embodiment, the P element 302 and the N element 304 of the thermoelectric couple 300 may be made of zero-dimensional quantum dots of lead-tin-selenium-telluride or another thermo-electric material. In another embodiment, the P element 302 and the N element 304 of the thermo-electric couple 300 may be made of one-dimensional nano wires of bismuth-antimony or another thermo-electric material. In yet another embodiment, the P element 302 and the N element 304 of the thermo-electric couple 300 may be made of two-dimensional quantum wells, or superlattice thermo-electric structures of silicon-germanium, boron-carbon or other thermo-electric materials. Arrangement of the low dimensional structures, relative to the flow of heat, may be in-plane or cross-plane.

It is understood that the structures and thermoelectric materials of the thermoelectric couple 300 are exemplary and not intended to be limiting. Other structures and thermo-electric materials may be included without departing from the principle and scope of the disclosed embodiments. For example, in certain embodiments, the thermo-electric couple 300 may include the P element 302 having different structures from the N element 304. For instance, the P element 302 may be made of zero-dimensional quantum dots, while the N element 304 may be made of two-dimensional quantum wells, or superlattice thermo-electric structures.

Referring back to FIG. 2, the power bus 206 may be used to direct electrical power from the power converter 208, the power supply 104 and/or the engine 108 to various systems of the machine 100 and/or the devices 106. Various electrical power sources/power storage devices may be connected to the power bus 206, such as, for example, the engine 108, the auxiliary power unit 200, and/or the power supply 104. The power bus 206 may be any type of bus known in the art to be suitable for the above operation. The power bus 206 may operate at any desired voltage level and may provide electricity for the devices 106 and/or other various systems (not shown) within and/or associated with the machine 100. In certain embodiments, the power bus 206 may operate at a voltage level of about 14.4V, 30V, 300V, or any other desired voltage level.

The power converter 208 may be any type of electronic device that accepts a DC input voltage and produces a DC output voltage at the same or different level than the input voltage. The power converter 208 may condition the voltage by regulating the input voltage and/or isolating noises on the input. Further, the power converter 208 may include control circuitry that can exchange data and control commands with the controller 210 or special hardware registers that can be set by the controller 210. The power converter 208 may operate automatically based on a default setting or operate under the regulation of the controller 210 to perform more complex operations. It is contemplated that the power converter 208 may perform other operations, as is known in the art.

The controller 210 may serve to control the operations of various components of the machine 100. The controller 210 may include devices suitable for running software applications. For example, the controller 210 may include a CPU, RAM, I/O modules, etc. (not shown). In one embodiment, the controller 210 may be configured to control the operation of the auxiliary power unit 200. For example, the controller 210 may regulate the fuel pumping arrangement 124 to direct fuel and air to the heater 122, the heater 122 to ignite the fuel/air mixture to generate heat within the exhaust passage 118 and/or the cooling system 110 to pressurize and direct coolant to the cooling jacket 202. As the thermo-electric device 204 generates electrical power from the temperature gradient created by the heater 122 and the cooling jacket 202, the controller 210 may regulate the power converter 208 to condition the generated power.

The controller 210 may be further configured to determine a load on the power bus 206. This load may include the power consumed by on-board electronics, on-board lighting, during a starting of the engine 108, and/or by other power demanding components associated with the machine 100. The load on the power bus 206 may be determined by observing the load on the different power producing devices connected to the power bus 206 (e.g., the engine 108 and the auxiliary power unit 200). For example, the load on the power supply 104 may be determined by observing the current drawn from the power supply 104 at a given time. From the current drawn from the power supply 104, the controller 210 may be configured to determine the power required from the power supply 104 to handle this load. The controller 210 may be configured to determine the difference between the total capacity of the power supply 104 and the load on the power supply 104 and to determine the amount of power available from the power supply 104 on the power bus 206 for the devices 106. The controller 210 may initiate operation of and disable the auxiliary power unit 200 based on the determined loads.

The auxiliary power unit 200 may be configured to operate independent of the engine 108. That is, when the engine 108 is non-operational (i.e., shut down), the auxiliary power unit 200 may produce the electrical power demanded by devices 106. In particular, the fuel pumping arrangement 124 may be controlled to supply fuel along with air from the air supply (not shown) to the heater 122, which may ignite the fuel/air mixture and direct flame jets toward the catalyst substrate 120. Substantially simultaneously, the cooling system 110 may be controlled to pressurize and direct coolant in the vicinity of the catalyst substrate 120 via the cooling jacket 202. The temperature difference between the cooling jacket 202 and the exhaust passage 118 may create a temperature gradient across the thermo-electric couple 300 that can be used to generate electrical power. Alternatively, or additionally, the auxiliary power unit 200 may be controlled to generate power when the engine 108 is operational, if desired. It is contemplated that the auxiliary power unit 200 may utilize exhaust from the engine 108 to further aid in generating heat when the auxiliary power unit 200 is utilized in conjunction with operation of the engine 108. Furthermore, it is contemplated that the catalyst substrate 120 may be selectively regenerated during production of power, if desired, whether or not the engine 108 is operational.

INDUSTRIAL APPLICABILITY

The disclosed auxiliary power unit may be incorporated to function with any machine's exhaust system to generate power, even when an associated primary mover is non-operational. The disclosed auxiliary power unit may be a cost effective and efficient substitute for a conventional auxiliary power unit used by on-highway long-haul machines. It is also contemplated that the disclosed auxiliary power unit may be a cost effective and efficient substitute for a conventional auxiliary power unit used by a generator set, a pump, or another stationary operation-performing machine. The operation of the auxiliary power unit 200 will now be explained below.

As the machine 100 is operated, a machine operator may desire to park the machine 100 overnight or for long periods of time during the day. During this time the machine operator may desire to use devices 106 to heat the cab 102, watch television, listen to a radio, etc. The operator may also desire to use devices 106 to perform maintenance on an interior and/or exterior of machine 100. Specifically, the auxiliary power unit 200 may be operated to meet the internal and/or external loads of the devices 106.

To generate electrical power for the devices 106, the controller 210 may regulate the fuel pumping arrangement 124 to supply a pressurized flow of fuel and air to the heater 122. The heater 122 may ignite the fuel/air mixture and direct heat toward the catalyst substrate 120, thereby warming the exhaust passage 118 and the catalyst substrate 120 (as is done to regenerate the catalyst substrate 120). The controller 210 may additionally control the cooling system 110 to circulate coolant through the cooling jacket 202.

The operation of heater 122 and the cooling system 110 may create a temperature gradient across the thermo-electric couple 300. The temperature gradient across the thermo-electric couple 300 may equate to a temperature difference AT between opposing junctions 306, 308, and 310 within the thermoelectric couple 300. The thermo-electric device 202 may utilize temperature difference ΔT to convert thermal energy into electrical energy based on the Seebeck effect. The thermal electric energy may be passed to the power converter 208 for conditioning, and the conditioned power may be passed to the power bus 206. The power bus 206 may direct the generated electrical power to the devices 106 and/or to the power supply 104 for storage. Regeneration of the catalyst substrate 120 may also occur during operation of the auxiliary power unit 200, if desired. That is, the catalyst substrate 120 may be regenerated while the heater 122 is warming the exhaust passage 118.

Alternatively, should the machine 100 embody a stationary machine, the auxiliary power unit 200 may generate power for electrical devices associated with the machine 100. Such electrical devices may embody, for example, one or more sensors configured to sense various parameters of the machine 100. However, it is contemplated that there are many various electrical devices that may be associated with a stationary machine, as is known in the art, which may also be powered by the auxiliary power unit 200.

The auxiliary power unit 200 may be cost effective because of the utilization of systems and devices already implemented on the machine 100. That is, because the machine 100 may already include the cooling system 110 and the exhaust system 116, few additional components may be needed. The disclosed system may be more efficient at generating power than idling the engine 108 or operating traditional auxiliary power units. This increased efficiency may be possible because of the use of low dimensional structures having high efficiencies. Further, the disclosed the auxiliary power unit 200 may create less noise than the idling of the engine 108 or the operation of the traditional auxiliary power unit. A reduction in noise may be desirable for the comforts of the machine operator and environment.

It will be apparent to those skilled in the art that various modifications and variations can be made to the auxiliary power unit of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the auxiliary power unit disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents. 

1. An auxiliary power unit, comprising: an exhaust passage configured to direct a flow of exhaust from a primary mover; a catalyst substrate disposed within the exhaust passage; a heater configured to heat the catalyst substrate; a cooling jacket associated with the exhaust passage; and a thermo-electric device disposed between the cooling jacket and the exhaust passage, the thermo-electric device being configured to generate electrical power from a temperature gradient created by the heater and the cooling jacket when the primary mover is non-operational.
 2. The auxiliary power unit of claim 1, further including an electric-powered fuel pumping arrangement configured to pressurize fuel directed to the heater.
 3. The auxiliary power unit of claim 2, wherein the heater is configured to direct pressurized fuel into the exhaust passage and ignite the pressurized fuel to heat the catalyst substrate.
 4. The auxiliary power unit of claim 1, wherein the thermoelectric device is configured to generate electrical power from the temperature gradient created by the heater and the cooling jacket when the primary mover is operational.
 5. The auxiliary power unit of claim 4, wherein the heater is turned off when the electrical power is generated during operation of a primary mover.
 6. The auxiliary power unit of claim 1, further including an electric pump configured to pressurize coolant directed to the cooling jacket.
 7. The auxiliary power unit of claim 1, wherein the heater is configured to regenerate the catalyst substrate.
 8. The auxiliary power unit of claim 1, wherein the thermo-electric device includes a thermoelectric material having zero-dimensional quantum dots.
 9. The auxiliary power unit of claim 1, wherein the thermoelectric device includes a thermoelectric material having one-dimensional nano wires.
 10. The auxiliary power unit of claim 1, wherein the thermo-electric device includes a thermo-electric material having one of two-dimensional quantum wells and superlattice structures.
 11. The auxiliary power unit of claim 1, wherein the thermo-electric device includes a thermo-electric material having a figure of merit ZT between about 1 and about
 10. 12. The auxiliary power unit of claim 1, wherein the thermo-electric device includes a P element and an N element made of differing thermo-electric materials.
 13. The auxiliary power unit of claim 1, wherein the thermo-electric device includes bulk thermo-electric materials.
 14. A method of generating auxiliary power, comprising: generating heat to warm an exhaust treatment device; directing the heat toward a thermoelectric material when a primary mover is non-operational; cooling the thermo-electric material to produce a temperature gradient across the thermo-electric material; and generating electrical power from the temperature gradient.
 15. The method of claim 14, wherein the exhaust treatment device is not regenerated when electrical power is generated from the temperature gradient.
 16. The method of claim 14, further including processing and storing the electrical power.
 17. The method of claim 14, further including generating electrical power from the temperature gradient when the primary mover is operational.
 18. The method of claim 14, further including generating electrical power from the temperature gradient when regenerating the exhaust treatment device.
 19. A machine, comprising: an engine configured to produce a power output directed toward moving the machine; an exhaust passage configured to direct a flow of exhaust; a catalyst substrate disposed within the exhaust passage; an electrically-powered fuel pumping arrangement configured to pressurize fuel; a heater configured to receive pressurized fuel from the fuel pumping arrangement and ignite the fuel to heat the catalyst substrate; an electrically-powered cooling system configured to pressurize and direct coolant to transfer heat from the engine; an auxiliary power unit configured to convert thermal energy to electrical energy and being operable when the engine is non-operational, the auxiliary power unit including: a cooling jacket associated with the exhaust passage; and a thermo-electric device disposed between the cooling jacket and the exhaust passage, the thermoelectric device being configured to generate electrical power from a temperature gradient created by the heater and the cooling jacket when the primary mover is non-operational.
 20. The machine of claim 19, wherein the thermoelectric device includes high efficient materials having at least one of a zero-dimensional quantum dots thermo-electric material, a one-dimensional nano wires thermo-electric material, a two-dimensional quantum well thermo-electric material, and a superlattice structured thermo-electric material. 